Self-Induced Polarization Rotation Effect of an Elliptically Polarized Beam in CuCl

The two-photon self-induced polarization rotation effect of an elliptically polarized laser beam is demonstrated experimentally in the giant two-photon absorption (GTA) region of \(\varGamma_{1}\) excitonic molecule in CuCl. The rotation angle of the principal axsis is found to be proportional to the incident beam intensity and sin 2ψ where ψ is its ellipticity angle. On the basis of a simplified four-level model, these characters are expressed quantitatively by the difference between the non-linear susceptibilities for the right- and the left-circularly polarized components of the elliptical polarized beam. The non-linear dispersion curve associated with the GTA resonance is determined.